Sopwith Snipe Project

[Balloon_Buster]

Un believable! There's no way I would ever consider doing such a project, but I'm glad to see that some would!

[Nick]

Could you make the fittings using mild steel, do they really need to be 4130?

Hi Baldeagle,
Good question, it's certainly much easier to bend than 4130 and it was good enough then so why not now. I guess I just wanted it to be as strong as possible as it will be my backside strapped into that wicker chair when the time comes
I'm not concerned about the fittings that I did get cracks in as they have been rewelded there plus all of the Spar Clips are designed with reinforcement lugs which are rivetted in place (3/16" steel rivets) then edge welded so effectively ends up twice the thickness. I think they're probably over engineered if anything.

Un believable! There's no way I would ever consider doing such a project, but I'm glad to see that some would!

Hi Balloon_Buster,
Thanks, I'll take that as a compliment rather than an observation on my sanity Actually I've found it a most enjoyable learning exercise, not only learning new skills but also tracking down some of the old instruments etc.

Cheers, Nick

[Joe Perkel]

Great thread Nick, productive subject matter.

On the subject of fittings and clips. Why the blue fittings on this Strutter in France?

Are these powder coated?

[Machinbird]

Nick, Just my opinion, but Baldeagle is asking a very valid question. We want our flying machines to be strong, not just on the first flight, but also out into the future.
If small bending cracks form and you do not re-weld them successfully by heating up the fitting with your torch, then the remaining defects become stress risers which will most likely grow with the application of stress cycles. Additionally, you may be creating heat affected zones (HAZ) adjacent to the areas you have rewelded which may also promote cracking.
If you really want stronger fittings using the 4130, and you have a bend radius sharp enough to cause cracking of the 4130, then perhaps bending them hot and normalizing the complete fitting might be a better way to go.
In general, avoidance of cracks, edge defects, and maintaining generous corner radii is sufficient to create a long fatigue life in a properly designed fitting. Anything that creates discontinuities in material properties should raise red flags.
If we can bend the fitting without cracking from mild steel with the desired corner radius, are we always making a better part by substituting 4130?

[Nick]

Nick, Just my opinion, but Baldeagle is asking a very valid question. We want our flying machines to be strong, not just on the first flight, but also out into the future.

Hi Syd,
Absolutely, it's a very valid question. The way I have gone about welding issues is that if it's not a structural part I will weld it up myself but if it's major parts like these I have just tacked them all up and handed them over to a Licenced aircraft welder. I simply wouldn't put that sort of faith in my welding at this stage.

Nick

[j ferguson]

Nick,
Wouldn't you wonder about the fittings that didn't crack? Might not they also have become embrittled in the fabrication but not exhibit cracking - yet? Is it possible as Sid suggests to have the non-welded ones normalized (heat treated to de-stress these bends)?

I suspect that once you cover your fuselage, many of these fittings will no longer be accessible. You may really have to rely on them holding up until you recover in maybe ten years.

Or maybe I just worry too much.

best regards, John Ferguson

[Nick]

Nick,
Wouldn't you wonder about the fittings that didn't crack? Might not they also have become embrittled in the fabrication but not exhibit cracking - yet? Is it possible as Sid suggests to have the non-welded ones normalized (heat treated to de-stress these bends)?

Hi John,
Am listening to you all here. I have spoken to the welder and they were all destressed however you've got me worried now. This problem only applied to the .080" spar clips of which there are 8 (the others are all .063" and no problem) so I will strip the paint off them and get them magnafluxed.
Thanks for the input

Cheers, Nick

[Nick]

Oh dear do I really have to strip all that paint off again? I guess I do

[Nick]

Just about finished the Main fairlead, this morning. Just have to flare the springs once they wont be disassembled again.
Am wondering about corrosion inside the housings as if I prime them and the sleeves before assembly they'll be too tight to assemble again as they just slide over. Maybe I can just dip them prior to tightening up?
Any ideas?




Cheers, Nick

[Machinbird]

Originally Posted by Nick

Any ideas?

Nick, It looks like a natural for electroplating. Any cryptic notes on the drawing?

You are doing a wonderful job on the Snipe. It is so good that I'm sure Tommy Sopwith would award you a data plate if he was still around.
Sid